Device for controlling an engine

Abstract: A device for controlling an engine (2) comprises a main control means (60) for outputting a control signal in response to a signal from an accelerator dial (22), and a sub-control means (40) for controlling an actuator (30) that actuates a control lever (6) of a fuel feeding means (4) in response to a control signal from said main control means (60) and a signal from a key switch SW. The sub-control means (40) controls said actuator (30) in response to an off signal from said key switch SW so that said control lever (6) is moved to a fuel stop position and, after the operation of the engine (2) has been halted, controls said actuator (30) so that said control lever (6) is moved to a start position.

Description: Field of the Invention The present invention relates to a device for controlling an engine and, particularly, to a device for controlling an engine mounted on a construction machine and the like machine. Description of the Prior Art Fig. 3 illustrates a conventional device for controlling an engine mounted on a construction machine and the like machine, wherein reference numeral 2 denotes an engine, and 4 denotes a fuel injection pump for feeding fuel to the engine 2. The amount of the fuel fed to the engine is determined depending upon the operation position of a control lever 6. The control lever 6 of the fuel injection pump is actuated by an actuator 14 which includes an electric motor 8, a reduction gear 10, an output lever 12, etc. The actuator 14 is controlled for its operation by a controller 16 which comprises a control unit 18 and a drive circuit 20. The control unit 18 outputs a control signal in response to a signal from an accelerator dial 22, a signal from a key switch 24 and a signal from a lever position sensor 26 that is mounted on the actuator 14 and detects the operation position of the control lever 6. The drive circuit 20 supplies the electric power to the actuator 14 in response to the control signal from the control unit 18. With the thus constituted device for controlling an engine, the key switch 24 is turned on at the time of starting the engine and the accelerator dial 22 is manipulated and is set to any position. Thereby, in response to a set position signal and a signal from the lever position sensor 26, the control unit 18 outputs a control signal to the drive circuit 20 which drives the electric motor 8, and the control lever 6 of the fuel injection pump is moved to a position that corresponds to the position to where the accelerator dial 22 is set. Then, the accelerator dial 22 is manipulated toward the direction of acceleration or deceleration, and the control lever 6 is operated between a low idling position L1 and a high idling position L2 in response to the manipulated position, thereby to adjust the speed of revolution of the engine. Next, to stop the engine, the key switch 24 is turned off. Thereby, the control unit 18 outputs the deceleration signal irrespective of the position to where the accelerator dial 22 is set, and the control lever 6 is moved to a fuel stop position L0 while confirming the signal from the lever position sensor 26. Thus, the fuel is no longer fed to the engine 2; i.e., the engine is brought into a halt. Here, however, the controller 16 equipped with the control unit 18 is not only controlling the actuator 14 that actuates the control lever 6 of the fuel'injection pump but also controlling other systems such as a hydraulic pump, control valve in a hydraulic circuit, illumination circuit, wiper blade driving circuit and the like circuits, and hence, is subject to undergo trouble at a high probability. When the controller 16 malfunctions, it becomes difficult to control the engine. When trouble with the controller 16 arises during the operation of the engine, in particular, the engine cannot often be brought into a halt, which is undesirable from the standpoint of safety. When the controller breaks down after the halt of the engine, the control lever 6 of the fuel injection pump cannot be moved from the fuel stop position LO; i.e., the engine cannot be started and the construction machinery is brought to a standstill in the site. US-A-5 131 358 relates to a control device using a magnet valve, the switching date thereof being determined by a switching contact of a diesel engine control device. The magnet valve controls an operating piston which displaces a control rod of a fuel injection pump which controls the quantity of fuel delivered to an internal combustion engine and, after being switched to a stop position, the control rod automatically arrives at a start position required for restarting the internal combustion engine. Summary of the Invention The principal object of the present invention is to provide a device for controlling an engine which is capable of bringing the engine into a halt by turning the key switch off even in case the controller gets out of order during operation of the engine and is capable of starting the engine even when the controller malfunctions after the halt of the engine. In order to accomplish the above-mentioned principal object according to the present invention, there is provided a device for controlling an engine, which comprises a main control means for outputting a control signal in response to a signal from an accelerator dial, and a sub-control means for controlling an actuator that actuates a control lever of a fuel feeding means which feeds fuel to the engine in response to a control signal from said main control means and a signal from a key switch, and in which said sub-control means controls said actuator in response to an off signal from said key switch so that said control lever is moved to a fuel stop position and, after the operation of the engine has been halted, control said actuator so that said control lever is moved to a start position, wherein said sub-control means is mounted on said actuator. In the device for controlling an engine according to the present invention, the main control means, during the ordinary operation, outputs an acceleration signal, a deceleration signal or a stop signal to the sub-control means in response to a signal from the accelerator dial and a signal from the control lever position sensor, and the sub-control means outputs a control signal to the drive circuit in response to a control signal from the main control means, whereby a forward/reverse electric motor that constitutes the actuator is driven and the control lever of the fuel injection pump is moved to a position that corresponds to the position to where the accelerator dial is manipulated. Then, to stop the engine, the key switch is turned off whereby the sub-control means controls the forward/reverse electric motor of the actuator so that the control lever is moved to the fuel stop position and, after the operation of the engine has been halted, controls the forward/reverse electric motor of the actuator so that the control lever is moved from the fuel stop position to the start position. Brief Description of the Drawings Fig. 1 is a block diagram of a device for controlling an engine constituted according to the present invention; Fig. 2 is a flow chart for illustrating the operation of a sub-control means that constitutes the device for controlling an engine of Fig. 1; and Fig. 3 is a block diagram of a device for controlling an engine that has been conventionally used. Detailed Description of the Preferred Embodiments A device for controlling an engine constituted according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings. Referring to Fig. 1 which illustrates a device for controlling an engine constituted according to an embodiment of the present invention, reference numeral 2 denotes a diesel engine, and 4 denotes a fuel injection pump which is a fuel feeding means for feeding fuel to the engine 2. The amount of fuel fed to the engine 2 is determined depending upon a position to where a control lever 6 is moved. The control lever 6 of the fuel injection pump 4 is controlled to move, by an actuator 30, between a low idling position L1 and a high idling position L2 and to a fuel stop position L0 and to a start position L3. The actuator 30 comprises a forward/reverse electric motor 32, a reduction gear 34 coupled to the output shaft of the motor 32, a rotary shaft 36 coupled to the reduction gear 34, and an output lever 38 which is coupled at its one end to the rotary shaft 36. The output lever 38 is connected at its other end to a link 28 that is coupled to the control lever 6. The thus constituted actuator 30 is served with the drive electric power from a drive circuit 50 that is controlled by a sub-control means 40. The sub-control means 40 outputs to the drive circuit 50 a control signal in accordance with a control program that is contained therein, in response to a signal from a main control means 62 that constitutes a controller 60 which is made up of a microcomputer and will be described later, a signal from a control lever position sensor 70, a signal from an engine revolution sensor 80, a signal from a key switch SW and like signals. The main control means 62 is made up of a microcomputer and outputs a control signal such as an acceleration signal, a deceleration signal or a stop signal to the sub-control means 40 in accordance with a control program contained therein in response to a signal from a dial accelerator made up of a potentiometer, a rotary switch and the like, a signal from a control lever position sensor 70 and like signals. The control lever position sensor 70 is constituted by a potentiometer, and detects the operation position of the control lever 6 through a rotational position of the rotary shaft 36 of the actuator 30 that operates correspondingly thereto, and outputs a detection signal to the main control means 62 and to the sub-control means 40. The engine revolution sensor 80 is disposed, for example, being opposed to the engine flywheel, to detect the speed of revolution of the engine, and outputs the detection signal to the sub-control means 40. In the illustrated embodiment, the sub-control means 40, the drive circuit 50 and the control lever position sensor 70 are mounted on the actuator 30. Next, described below is the operation of the device for controlling an engine that is constituted according to the embodiment as described above. The main control means 62 inputs a signal from the accelerator dial 22 and a signal from the control lever position sensor 70, judges whether it is the acceleration or the deceleration or the both are in agreement based upon the manipulated position of the accelerator dial 22 and the position to where the control lever 6 is moved, and outputs a control signal to the sub-control means 40. When the key switch SW is turned on, the sub-control means 40 inputs a control signal from the main control means 62, and outputs, as a control signal to the drive circuit 50, a forward rotation signal in the case of the acceleration, a reverse rotation signal in the case of the deceleration or a stop signal when the manipulated position of the accelerator dial 22 is in agreement with the position to where the control lever 6 is moved. In response to a control signal from the sub-control means 40, the drive circuit 50 supplies the electric power to the forward/reverse electric motor 32 of the actuator 30 or stops supplying the electric power. With the forward/reverse electric motor 32 of the actuator 30 being controlled as described above, the control lever 6 is moved to a position corresponding to the manipulated position of the accelerator dial 22 between the low idling position L1 and the high idling position L2, and the fuel of an amount corresponding to the operation position is fed from the fuel injection pump 4 to the engine 2. Next, described below is the operation of the sub-control means 40 of when the operation of the engine 2 is brought into halt with reference also to a flow chart of Fig. 2. In the sub-control means 40, when it is confirmed that the key switch SW is turned off (step S1), the program proceeds to a step S2 to read a detection signal L from the control lever position sensor 70. Then, it is checked at a step S3 whether a control lever position L is equal to the fuel stop position L0 or not. When the control lever position L is equal to the fuel stop position L0 at the step S3, no fuel has been fed; i.e., the engine 2 has been halted already and there is no need of executing the operation to stop the engine. Therefore, the program is finished. When the control lever position L is not equal to the fuel stop position L0 at the step S3, the engine is in operation. In order to stop the engine, therefore,the forward/reverse electric motor 32 of the actuator 30 is driven in the reverse direction (step S4). When the electric motor 32 is reversely driven, the sub-control means 40 proceeds to a step S5 to read a detection signal L from the control lever position sensor 70. At a step S6, it is checked whether the control lever position L is equal to the fuel stop position L0 or not. When the control lever position L is not equal to the fuel stop position L0, the control lever 6 is not still arriving at the fuel stop position L0. Therefore, the operations of from the step S4 to the step S6 are repeated. When the control lever position L becomes equal to the fuel stop position L0 at the step S6, the electric motor 32 is no longer driven (step S7), an engine revolution signal N is read out from the engine revolution sensor 80 (step S8), and it is confirmed whether the engine revolution N has become zero (0) or not (step S9). This is to make sure that the revolution due to the force of inertia has reliably come into a halt, since the engine is revolving due to the force of inertia even after the control lever position L has moved to the fuel stop position L0 to stop the supply of fuel to the engine 2. When the engine revolution N is not still zero (0) at the step S9, the engine revolution N is waited for until it becomes zero (0). When it is confirmed that the engine revolution N became zero (0), the sub-control means 40 drives the forward/reverse motor 32 in the forward direction (step S10). When the motor 32 is driven in the forward direction, the sub-control means 40 proceeds to a step S11 to read a detection signal L from the control lever position sensor 70. It is then checked at a step S12 whether the control lever position L is equal to the start position L3 or not. When the control lever position L is not equal to the start position L3 at the step S12, the control lever 6 does not still arrive at the start position L3. Therefore, the operations of from the step S10 to the step S12 are repeated. When the control lever position L becomes equal to the start position L3 at the step S12, the electric motor 32 is no longer driven (step S13). According to the illustrated embodiment mentioned above, when the key switch SW1 is turned off, the sub-control means 40 works to reversely drive the electric motor 32 of the actuator in order to move the control lever 6 of the fuel injection pump 4 to the fuel stop position L0 irrespective of the control signal from the main control means 62. Therefore, the engine 2 can be reliably brought into a halt even in case the main control means 62 gets out of order. When the engine is to be stopped, the sub-control means 40 works to move the control lever 6 to the fuel stop position L0 to reliably bring the engine into a halt, and thereafter, works to forwardly drive the electric motor 32 of the actuator 30 so that the control lever 6 is brought to the start position L3. Therefore, even in case the main control means 62 is out of order at the time of starting the engine again, the fuel is supplied, by cranking, in an amount necessary for starting the engine; i.e., it is allowed to start the engine. The illustrated embodiment has employed an engine revolution sensor 80 as a means for making sure that the revolution of the engine has become zero (0). It is, however, also allowable to make sure the halt of the engine revolution by providing a timer to count a predetermined period of time after the control lever 6 of the fuel injection pump 4 is moved to the fuel stop position L0. As described above, the device for controlling an engine according to the present invention comprises a main control means for outputting a control signal in response to a signal from an accelerator dial, and a sub-control means for controlling an actuator that actuates a control lever of a fuel feeding means in response to a control signal from said main control means and a signal from a key switch, and said sub-control means controls said actuator in response to an off signal from said key switch to move said control lever to a fuel stop position and, after the operation of the engine has been halted, controls said actuator to move said control lever to a start position. Therefore, even in case the main control means gets out of order, the engine can be reliably brought into a halt by the sub-control means. This makes it possible to solve the problem in that the engine cannot be stopped due to a trouble in the main control means during construction operations using a vehicle of construction machine. When the engine is to be stopped, furthermore, the sub-control means works to move the control lever to the fuel stop position to reliably bring the engine into a halt and, thereafter, works to move the control lever to the start position. Therefore, even in case the main control means get out of order after the engine has been stopped, the fuel can be supplied, by cranking, in an amount necessary for starting the engine; i.e., the engine can be started and the machine can be moved. Since the control lever is moved to the start position after the engine has been brought into a halt, the engine can be started again even in case the battery power which is the power source is lowered, and, besides, the cranking can be shortened by a period of time in which the control lever is moved from the fuel stop position to the start position. In assembling the machine at a production plant, furthermore, the controller is usually mounted at the final stage. Without the controller being mounted, the engine can be neither started nor stopped. According to the present invention, however, the sub-control means is mounted on the actuator, making it possible to start and stop the engine as mentioned above and, hence, to check the operations of the engine and the hydraulic systems, enabling the production efficiency to be enhanced.

Claims: Apparatus for controlling an engine (2), which comprises a main control means (60) and a sub-control means (40) for controlling an actuator (30) that actuates a control lever (6) of a fuel feeding means (4) which feeds fuel to the engine (2) in response to a control signal from said main control means (60) and a signal from a key switch SW, and in which said sub-control means (40) controls said actuator (30) in response to an off signal from said key switch SW so that said control lever (6) is moved to a fuel stop position and, after the operation of the engine (2) has been halted, controls said actuator (30) so that said control lever (6) is moved to a start position, characterized in that the main control means outputs the control signal in response to a signal from an accelerator dial (22), wherein said sub-control means (40) is mounted on said actuator (30). Method for controlling an engine (2) with the following steps: outputting a control signal in response to a signal from an accelerator dial (22) by a main control means (60), controlling by a sub-control means (40) an actuator (30) that actuates a control lever (6) of a fuel feeding means (4) which feeds fuel to the engine (2) in response to a control signal from said main control means (60) and a signal from a key switch SW, controlling by said sub-control means (40) said actuator (30) in response to an off signal from said key switch SW so that said control lever (6) is moved to a fuel stop position and so that, after the operation of the engine (2) has been halted, said control lever (6) is moved to a start position, wherein said sub-control means (4) is mounted on said actuator (30).

Inventors: KUWABARA TOSHIO, MATSUBARA MORIHIKO, OKANO SHUJI, KUWABARA, TOSHIO, MATSUBARA, MORIHIKO, OKANO, SHUJI, KUWABARA, TOSHIO, C/O SHIN CATERPILLAR, MATSUBARA, MORIHIKO, C/O SHIN CATERPILLAR, OKANO, SHUJI, C/O SHIN CATERPILLAR
Applicants: CATERPILLAR MITSUBISHI LTD, SHIN CATERPILLAR MITSUBISHI LTD.
Application year: 1994
Main classification: F02D11
IPC codes: F02D41, F02D31, F02D11